The present invention is drawn to a method for the treatment of foundry sand and/or core sand which is fed as a sand mould to a moulding plant and is subsequently, after metal casting has taken place, separated from the cast piece at an emptying station.
For producing cast pieces, moulds formed from foundry sand are commonly used. Due to the thermal effect of the liquid metal being cast, the sand is partly destroyed because of the binding agent used, for example bentonite, which burns due to the high temperatures of the liquid metal. The destroyed sand must be taken out of the cycle. By the addition of new sand in the form of cores, which serve to form the hollow spaces in the cast pieces, continuously fresh new sand is supplied to the system.
The excess sand must then be removed from the system and taken away to the waste tip. This so-called waste or used sand also contains, besides the sand (generally silica sand), moulding material admixtures such as bentonite and carbon carriers. Because of these admixture materials, the possibilities for re-use of waste sand in other areas (in building industry among other things) is limited. The used sand accumulating at foundries in the manner described above is therefore taken to waste tips.
Considered statistically, approximately 580 kg of used sand occur per ton of casting produced. Besides the economic disadvantages for the foundries themselves, the environmental burden necessitated by the disposal of the accumulating used sand is considerable.
Accordingly, it is the principle object of the present invention to provide a method for the economic re-use of the used sand. It is a further object of the present invention to achieve a substantial reduction in the environmental burden, in that the waste to be taken to the waste tip is reduced to a minimum.